On Thursday, MLB released a statement about Castillo’s PED violation and suspension.

The Office of the Commissioner of Baseball announced today that Chicago White Sox catcher Welington Castillo has received an 80-game suspension without pay after testing positive for Erythropoietin (EPO), a performance-enhancing substance, in violation of Major League Baseball’s Joint Drug Prevention and Treatment Program.

The suspension of Castillo is effective immediately.

As Ken Rosenthal originally said on Twitter, Castillo was caught using a PED, but not a steroid. Erythropoietin, a hormone produced by the kidneys, is used for blood doping. It stimulates the production of red blood cells, which carry oxygen from the lungs to the rest of the body — including muscles. Oxygen fuels the muscles, so more red blood cells means more oxygen, which can help muscles perform better.

White Sox general manager Rick Hahn released a statement on Thursday as well.

I was recently notified by Major League Baseball that I had tested positive for EPO, a substance that is prohibited under MLB’s Joint Drug Agreement. The positive test resulted from an extremely poor decision that I, and I alone, made. I take full responsibility for my conduct. I have let many people down, including my family, my teammates, the White Sox organization and its fans, and from my heart, I apologize. Following my suspension, I look forward to rejoining my teammates and doing whatever I can to help the White Sox win.

Castillo was in the White Sox starting lineup Wednesday when they faced off against one of his former teams, the Baltimore Orioles. He finished the game 1 for 5 with two strikeouts. Chicago won the game 11-1.

The 30-year-old veteran hit a career best 20 home runs for Baltimore last season. He signed a two-year, $15 million deal with Chicago last December. This season, he’s a .272 hitter with six homers and 15 RBIs. If all games are played as scheduled, Castillo will be eligible to return to the White Sox lineup on August 23.